Both 94s sinked at 20kg/h at idle

[flatjack9]

Originally Posted by Tinker

To my previous understanding and talks. There is/are 3.5 pvs installed, which is typical. Two 94 carbs share the pv vacuum and should equal 7.5in, Give or take. Less then half total vacuum of 18-20in at intake at idle. Low vacuum to properly open pv's and to "flood" gas, under-load or add fuel at speed (when the butterfly's are at their most open and draining the engine of inner vacuum/air) ...hence is when vacuum is low and fuel is needed. If all is working well... To my understanding anyway.


If initial engine vacuum at intake is too low. 94 pvs will open which allowing them to flood out an engine.


Thinking something else might be going on here a



.

I'm not understanding your comment concerning 7.5". The power valve sees whatever vacuum the engine is producing. If the vacuum is 17", each power valve sees that amount.

[flatjack9]

Originally Posted by Tinker

Nope, Vacuum can only be made with air flow. There is no vacuum with the engine off.


Vacuum drops when the engine has too much airflow. or when there is a leak, bad valves seating, or butterflies are open.


Make sense?


.

Actually air flow is caused by atmospheric pressure.

[Black Fifty]

Originally Posted by RandyMettler

Tinker, In response to your comment, "Less then half total vacuum of 18-20in at intake"

I am sending my 94s to Charlie. Your comment is what I have been mentioning previously. I am getting 20 at each carb simultaneously. I would think that would dictate I have a total of 40 intake vacuum which would be twice what is normal? Still learning all this. Vacuum and the throttle plate position is what draws fuel from the carburetors? (Air fuel mixture). If I have twice the vacuum would I be drawing twice the fuel?

The uni-syn is measuring mass air flow and giving you the result in kg/hr. You can convert that to "cfm" and that also tells you how much air is going into the engine while idling. I found a formula that converts kg/hr to cfm by multiplying your flow number by 2.08. 2.08 x 40 (carbs combined) tells you that the engine is getting 83.2 cfm at that engine speed. Or 41.6 cfm per carb. I would guess that having that "balance" makes for better volumetric efficiency of the engine by maximizing the likelihood that you'll get the same amount of air into each cylinder (in a perfect world).



Just my two cents.

Very interesting discussion too.
Mike

[Tinker]

Originally Posted by flatjack9

I'm not understanding your comment concerning 7.5". The power valve sees whatever vacuum the engine is producing. If the vacuum is 17", each power valve sees that amount.

Yes. When vacuum is below 7.5" the pv opens on a single holley94. 2 carbs split the number or close. My understanding.



More nonsense to add...

https://www.jalopyjournal.com/forum/...-valve.798600/

[Tinker]

Originally Posted by flatjack9

Actually air flow is caused by atmospheric pressure.

A flathead sitting has no atmospheric pressure on it, till it runs creating flow/pressure. But like blowing through a straw if you don't put your finger over the end then no pressure is made either.

I do have a barometer in my house though.






.

[flatjack9]

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Originally Posted by Tinker

Yes. When vacuum is below 7.5" the pv opens on a single holley94. 2 carbs split the number or close. My understanding.



More nonsense to add...

https://www.jalopyjournal.com/forum/...-valve.798600/

2 carbs do not split the vacuum. If the vacuum is 7.5" they both see that number. Standard power valves are rated at 7.5". When you install 3.5 power valves, that is where they will open.

[flatjack9]

Originally Posted by Tinker

A flathead sitting has no atmospheric pressure on it, till it runs creating flow/pressure. But like blowing through a straw if you don't put your finger over the end then no pressure is made either.

I do have a barometer in my house though.






.

This must be a new science. What does that barometer measure?

[Tinker]

Originally Posted by flatjack9

This must be a new science. What does that barometer measure?

Your sarcasm is not lost.


but just encase.
https://www.youtube.com/watch?v=i2UKTpIQG6M


https://www.youtube.com/watch?v=4K_XJGuRy88


neat version
https://www.youtube.com/watch?v=EkDhlzA-lwI

[Tinker]

Originally Posted by flatjack9

2 carbs do not split the vacuum. If the vacuum is 7.5" they both see that number. Standard power valves are rated at 7.5". When you install 3.5 power valves, that is where they will open.

Yes, being there is twice the air flow, 2 carbs vs 1. Like having two holes in a dam. So vacuum decreases quite quickly. Needing pv's that open at lower vacuum.


An engine that is working well at 18-20" vacuum at idle. Once you accelerate, it decreases engine vacuum. One carburetor only lets so much air flow through the engine. Two carburetors add more flow, etc. More flow less and less vacuum. Vacuum shared by each pv or carb.


pv's on 94s are reverse thinking. They close under vacuum and open under low vacuum conditions. Not a fan.




.

[Black Fifty]

neat version
https://www.youtube.com/watch?v=EkDhlzA-lwI


Now I see why so many hot rodders lower their cars. The pressure pushing down into the carbs will be higher at lower elevation. Fascinating!